No matter what you ask them, they'll have an answer; asking them questions doesn't really provide a good assessment of the realtor. (There are all sorts of online lists of questions to ask prospective realtors.)
Couple things to notice.
How responsive are they when you phone or email?
Do they use modern, efficient communication techniques?
How many listings do they have? Are they full time serious realtors, or is real estate their hobby or second job?
Here's one I liked about my realtor. I am looking at comps for a home I am interested in. Maybe the home I'm interested in is going for $250/sqft. A model match across the street sold two months ago for $230/sqft. I ask him why. If he knows and provides details, that's good.
Ask him if he knows of any pocket listings.
Does he need a GPS to get to addresses? Or, is he so familiar he already knows where the listings are?
If he knows the story behind an existing short sale, that's good. For example, he knows who the lender is, how many lenders there are, and how many backup offers there are.
I think it really comes down to your gut. How do you feel and engage with them? Do you feel like they're talking over you? Would you want him as a next door neighbor? Would you want him to marry your sister?